Activated carbon absorbent with integral heat transfer device

ABSTRACT

An integral adsorbent-heat exchanger apparatus for use in ammonia refrigerant heat pump systems. The apparatus has a finned tube heat exchange member. A bonded, pyrolyzed activated carbon adsorbent matrix, formed from a mixture of activated carbon particles and resol bonder, is tightly adjoined to the fins and the tube to form an integral apparatus. The integral apparatus is capable of withstanding repetitive adsorption and desorption cycles without the matrix becoming unbonded and without the matrix becoming unadjoined from the fins and tube. The apparatus permits very high rates of adsorption and desorption of refrigerant and very high rates of heat transfer between the refrigerant and the heat transfer fluid.

ORIGIN OF INVENTION

The invention described herein was made in the performance of work undera NASA contract, and is subject to the provisions of Public Law 96-517(35 USC in which the Contractor has elected to retain title.

BACKGROUND OF THE INVENTION

1. Technical Field

The field of this invention is heat pump systems and heat transferelements useful in such systems. The heat transfer elements of thisinvention are finned tube heat exchanger member having as an integralpart thereof an activated carbon adsorbent.

2. Discussion of the Invention

Heat pump systems have the advantage over conventional air conditioningsystems in that they can function as heating units in the winter months.

To maximize the efficiency of heat pump systems, for example suchsystems as those described in U.S. Pat. Nos. 5,042,259 and 5,046,319, itis desirable to improve the heat transfer rate between the fluids, forexample between the refrigerant or working fluid and the heat transferfluid. Various heat exchanger designs are commercially available fortransfer of heat between fluids. U.S. Pat. No. 4,709,558 discloses afinned tube heat exchanger member having an adsorbent in the spacebetween fins.

U.S. Pat. No. 4,999,330 discloses a process for forming high densityactivated carbon in cast or molded forms using PVA or methylcellulose asa binder. Methods of making moldable forms of activated carbon aredisclosed in U.S. Pat. No. 5,043,310.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an adsorbent-containingheat exchanger element for the very rapid adsorption and desorption ofammonia as refrigerant or working fluid, and for the very rapid transferof heat between the ammonia and heat transfer fluid. To preventdeterioration of the refrigerant and the adsorbent, the ammonia must notreact with the adsorbent or the metal parts of the heat exchanger. Forthe system to be efficient the adsorbent must also be adjoined to thesurface of the metal parts of the heat exchanger in good thermal contacttherewith, and most importantly, in such a way that the adsorbent doesnot, as a consequence of high frequency of heat andadsorption-desorption cycling (i.) become loose and forfeit good thermalcontact, or (ii.) powder, flake off or breakup and fall off the metalparts of the heat exchanger.

Because of their relatively low surface area, materials such as silicagels, zeolites and alumina are not good choices as adsorbent. It isknown, however, that pure activated carbon does not react with ammoniaand has relatively high surface area. Unfortunately pure activatedcarbon particles can not be used because they would fall away from themetal parts of the heat exchanger and not provide the necessary goodthermal contact desired. Various binders have been used to moldactivated carbon particles into various shapes. Unfortunately many ofthe binders, while providing good binding characteristics, will reactwith ammonia and therefore can not be used in systems using ammonia asthe refrigerant or working fluid. It will also be appreciated thatmechanical means, such as very fine mesh screens, or small orifice inletand outlet to otherwise sealed adsorbent chambers, can seriously retardthe rate of adsorption and desorption of refrigerant or working fluidand can result in low relative thermal conductivity of sorbent.Therefore for the adsorbent-heat exchanger device to be most useful, themeans for retaining the adsorbent in the device should not retard therates of refrigerant adsorption and desorption or the rates of heattransfer.

Therefore, it is important in heat pump systems that the adsorbent-heattransfer element can rapidly adsorb and desorb refrigerant and rapidlytransfer heat between the refrigerant and the heat transfer fluid.Commercial value can be likened to a pie eating contest in which the onewho can eat the most, the fastest, wins. In the case of heat pumpsystems, the system that sorb and desorb refrigerant the fastest andtransfer heat from the refrigerant to the heat transfer fluid thefastest, other factors being held constant, will have a commercialadvantage over other systems. Each cycle of the sorption-desorption islike one bite of the pie. Rather, however, instead of one bite of pie,there is one gulp of a quantity of heat. Unlike the pie eating champion,however, the commercially successful heat transfer device does not havethe luxury of a time to recover but must instead continue to adsorb anddesorb refrigerant and to transfer heat indefinitely.

The problem in heat pump systems is to provide adsorbent-heat transferelements which will rapidly adsorb and desorb refrigerant and yet beinexpensive so that the system can compete with conventional freon basedair conditioners.

In systems using ammonia, the adsorbent, and the structural materials ofthe heat transfer units which are exposed to ammonia, must not reactwith the ammonia. A chemically acceptable adsorbent is pure activatedcarbon. Acceptable structural materials are aluminum and stainlesssteel. Since ammonia will react with copper, this metal can not be usedwith ammonia based refrigerant systems if the ammonia will have directcontact with the copper.

Therefore, it is also an object of this invention to provide a finnedtube heat exchanger member having an activated carbon adsorbent adjoinedto the fin and outside surface of the tube surface which can effect andwithstand rapid adsorption and desorption of refrigerant and rapid andlarge swings in temperature without deteriorating and loosing goodthermal contact between the adsorbent and the metal parts of the heatexchanger device. Another object of this invention is to provide a heattransfer element having a long life cycle to eliminate, or minimize,replacement of the element over the life of the heat pump system. Yetanother object of this invention is to provide an inexpensive heattransfer element for use in heat pump systems.

In this invention excellent thermal contact between activated carbonparticles and between the activated carbon particles and the metal partsof the heat exchanger device are achieved thereby enabling very highrates of refrigerant adsorption and desorption and heat transfer to beachieved.

Accordingly there is provided by the principles of this invention anintegral apparatus for the transfer of heat having a tube part and a finpart, the fin part being in direct contact with the tube part andoutwardly thereof, the fin part forming a plurality of spaced apart finsand spaces along the tube part between the fins; and an activated carbonadsorbent in the spaces, adjoined to the fins and the tube part to forman integral apparatus.

In one embodiment the fin part is aluminum. In another embodiment thetube part is aluminum. In still another embodiment the tube part isstainless steel. In a further embodiment the fin part of the finned tubeheat exchanger member is aluminum and comprises an annular member, whichsurrounds the tube part, and to which the fins are attached. In apreferred embodiment the fins extend in a direction perpendicular to theaxis of the tube part. The activated carbon part of the integralapparatus is made from activated carbon particles, activated carbongranules, pre-shaped activated carbon forms, or combinations of suchforms of activated carbon. In another embodiment the activated carbonadsorbent comprises pre-shaped activated carbon forms made fromactivated carbon particles.

In one embodiment the activated carbon adsorbent in the spaces betweenthe fins is adjoined to the fins and the tube part by a process whichcomprises placing activated carbon and an adjoining agent into thespaces, and thereafter, subjecting the apparatus with the mixture in thespaces to an elevated temperature operable for causing the adjoiningagent to adjoin the activated carbon to the fins and to the tube part.In one embodiment the elevated temperature is between about 400° C. andabout 600° C. In another embodiment the elevated temperature is at leastabout 400° C. but below the temperature at which the metal of the finweakens. In still another embodiment the elevated temperature iseffected by heating the apparatus at a rate of about 100° C./hr under anon-deleterious atmosphere until a peak temperature of about 600° C. isreached, and thereafter, maintaining the apparatus at the peaktemperature for about 10 to about 20 hrs.

In still another embodiment the process of adjoining the activatedcarbon to the fins and the tube part, i.e. the metal parts, comprisesplacing a mixture which comprises a binder having a carbon basedmolecular structure, and particles of activated carbon, into the spaces,and thereafter, subjecting the apparatus with the mixture in the spacesto an elevated temperature operable for pyrolyzing the binder, and foradjoining the activated carbon particles to each other and to the metalparts. In one embodiment the binder is resol. In another embodiment theplacing of the mixture into the spaces comprises pressing the mixtureunder an elevated pressure of at least about 690 kPa (100 psi). In apreferred embodiment the pressing pressure is at least about 3450 kPa(500 psi) and in an especially preferred embodiment the pressingpressure is at least about 6900 kPa (1000 psi).

In still another embodiment the process of adjoining the activatedcarbon to the metal parts comprises pressing a mixture which comprises abinder having a carbon based molecular structure, a solvent for thebinder, and particles of activated carbon, into the spaces, thereafter,removing an effective amount of the solvent from the mixture operablefor allowing the mixture to be pyrolyzed to a density of at least about0.3 g/cc while remaining in the spaces, and thereafter, pyrolyzing thebinder to adjoin the activated carbon particles to each other and to themetal parts. In one embodiment the solvent is selected from the groupconsisting of alcohols, ketones and mixtures thereof. In anotherembodiment the solvent is isopropanol.

In yet another embodiment the process of adjoining the activated carbonto the metal parts comprises forming a first mixture which comprises abinder having a carbon based molecular structure and a solvent for thebinder, forming a second mixture which comprises a solvent and particlesof activated carbon, and adding an effective amount of the first mixtureto the second mixture operable for causing the first mixture to wet theactivated carbon particles of the second mixture thereby forming a thirdmixture. Thereafter, removing an effective amount of solvent from thethird mixture operable for producing a mixture of lower solvent contentwhich can be pressed into the spaces without exuding a large amount ofsolvent. This prevents loss of binder in the mixture prior to pyrolysis.Next, the mixture of lower solvent content is pressed into the spaces.Thereafter, with the mixture pressed into the spaces, removing aneffective amount of solvent from the mixture operable for allowing themixture to be pyrolyzed to a density of at least about 0.3 g/cc whileremaining in the spaces, and then, pyrolyzing the binder to adjoin theactivated carbon particles to each other and to the metal parts.

In a further embodiment the process for adjoining the adsorbent to themetal parts further comprises, after adding the first mixture to thesecond mixture and before removing solvent from the mixture, adding aneffective amount of a solvent to the third mixture to adjust theviscosity of the mixture to between about 10,000 and about 500,000poise. This additional step improves the distribution of the binder overthe activated carbon particles.

In one embodiment the process for adjoining the adsorbent to the metalparts further comprises adjusting the weight ratio of solvent-to-binderin the first mixture to a value between about 0.5 and about 5. Inanother embodiment the adjoining process further comprises adjusting theweight ratio of solvent-to-activated carbon in the second mixture to avalue between about 0.1 and about 5. In still another embodiment theadjoining process comprises adjusting the weight ratio ofbinder-to-activated carbon in the third mixture to a value between about0.05 and about 0.5.

In yet a further embodiment the process for adjoining the adsorbent tothe metal parts further comprises adjusting the weight ratio ofsolvent-to-activated carbon in the third mixture to a value betweenabout 0.5 and about 6, and the weight ratio of solvent-to-binder thereinto a value between about 6 and about 10.

In a preferred embodiment the process for adjoining the adsorbent to themetal parts further comprises adjusting the solvent-to-binder weightratio in the first mixture to a value between about 1.8 and about 2.4,adjusting the solvent-to-carbon weight ratio in the second mixture to avalue between about 0.7 and about 1.3, and adjusting thebinder-to-carbon weight ratio in the third mixture to a value betweenabout 0.2 and about 0.3. Thereafter, adding an effective amount of asolvent to the third mixture to adjust the solvent-to-carbon weightratio to a value greater than about 1.9 but less than about 2.3 andmixing to improve the distribution of binder on the activated carbonparticles, and then, reducing the solvent-to-carbon weight ratio to avalue between about 1.7 but less than about 2.

In an especially preferred embodiment the process for adjoining theadsorbent to the metal parts further comprises adjusting thesolvent-to-binder weight ratio in the first mixture to a value betweenabout 2 and about 2.2, adjusting the solvent-to-carbon weight ratio inthe second mixture to a value between about 0.9 and about 1.1, andadjusting the binder-to-carbon weight ratio in the third mixture to avalue between about 0.22 and about 0.28. Thereafter, adding an effectiveamount of a solvent to the third mixture to adjust the solvent-to-carbonweight ratio to a value greater than about 2 but no greater than about2.2 and mixing to improve the distribution of binder on the activatedcarbon particles, and then, reducing the solvent-to-carbon weight ratioto a value less than about 1.95.

In a further embodiment the process for adjoining the adsorbent to themetal parts further comprises painting a solvent containing dissolvedresol on the outside surface of the pyrolyzed adsorbent, and thereafter,subjecting the apparatus to an elevated temperature operable forpyrolyzing the resol on the outside surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a section of an integral adsorbent-heatexchanger device of this invention.

FIG. 2, is a graph of Thermal-Gravimetric-Analyzer test usingRefrigerant 22 ("R22") as the sotbate.

FIG. 3 is a graph of Thermal-Gravimetric-Analyzer test using R22 ontoAnderson AX-21 activated carbon without a binder. FIG. 4 is across-sectional view of the complete apparatus of FIG. 1.

FIG. 5 is a cross-sectional view of a section of a spiral aluminumfinned extrusion on an inner tube similar to FIG. 1.

FIG. 6 is graph of test data demonstrating the improved heat transferrate achievable with the adsorbent-heat exchanger device of thisinvention.

FIG. 7A is a cross-sectional view which illustrate another embodiment ofthis invention in which the fin part extends outwardly from the centraltube part, and also extends in a direction which is both perpendicularto, and longitudinal to, the axis of the tube part.

FIG. 7B is a cross-sectional view through line 7--7 of FIG. 7A whichillustrates that the fins extend outwardly in spoke-like fashion fromthe central tube part.

FIG. 8A is a cross-sectional view which illustrate yet anotherembodiment of this invention in which the fin part extends inwardly fromthe tube part, and also extend in a direction which is bothperpendicular to, and longitudinal to, the axis of the tube part.

FIG. 8B is a cross-sectional view through line 8--8 of FIG. 8A whichillustrates that the fins extend inwardly from the tube part.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention combines a resol binder with activated carbon usingisopropanol to dissolve the thick resol and enable adequate mixing. Theisopropanol is then partially evaporated, and the resulting thicktar-like mixture, is then pressed and molded into an inexpensive finnedaluminum tube extrusion. The extrusion with the in-place activatedcarbon is then dried and pyrolyzed in a nitrogen atmosphere at about600° C. for at least 24 hours to form an integral adsorbent-heatexchanger device 10 as illustrated in FIG. 1.

The remaining isopropanol is therefore fully evaporated and the resoldecomposed, leaving behind a carbon skeleton that holds the activatedcarbon particles together and in intimate contact with, and adjoined to,the aluminum, thereby forming an integral apparatus that enablesachievement of very high rates of heat transfer between the carbon andthe aluminum.

The center of the aluminum extrusion is hollow, thus allowing for a heattransfer fluid, such as water or Dowtherm™ heat transfer fluid, torapidly heat or cool the aluminum extrusion and integral activatedcarbon body adjoined thereto.

A process for adjoining the activated carbon to the aluminum extrusionis follows. Approximately 90 grams (90 g) of Anderson AX-21 dryactivated carbon was mixed with 90 g of isopropanol which resulted in amixture similar in viscosity to moist sand. Separately, approximately 11g of resol were mixed with 57 g of isopropanol, resulting in a veryflowable resol-containing liquid. The resol solution was then mixed withthe wetted activated carbon and stirred. Approximately 68 g more ofisopropanol was added to the mixture and stirred which resulted in amixture having the consistency of a loose, tar-like mixture which couldbe well mixed.

The isopropanol in the mixture was allowed to evaporate resulting in aweight loss of about 17 g and producing a mixture having a consistencylike that of thick tar to allow subsequent pressing without a large lossof dissolved binder in the solvent.

This mixture was then pressed into spaces between fins 11 of aluminumextrusion 12 as illustrated in FIG. 1. The fin diameter was 2.65 inches(2.65"), and internal tube 13 was 1.65" long and 1.25" in diameter.There were approximately 9.5 fins per inch having an average finthickness of about 0.018". A pressure of about 1000 psi over a period ofabout 5 minutes, was applied to the activated carbon-filled fins.

The excess activated carbon from outside of the finned area was removed,and unit was allowed to air dry for several days at about 40° C. toenable achievement of good ultimate adsorbent matrix density. Theassembly was then heated to 600° C. with a dry nitrogen purge. Theheating rate was approximately 100° C. per hour until 600° C. wasreached. Thereafter, a temperature of 600° C. was maintained for about18 hours. The resulting unit, as shown in FIG. 1, was a bonded activatedcarbon matrix 14 that was adhered to the aluminum fins and outside ofthe tube body thereby forming an integral adsorbent-heat exchangerdevice 10.

Some unanticipated longitudinal circumferential cracks 15 occurred inthe activated carbon matrix which extended from the outside diameter ofthe matrix to the tube as illustrated in FIG. 1. The cracking did notinterfere with the adhesion of the adsorbent matrix to the metal partsor the integrality of the adsorbent-heat exchanger device. It wasnoticed, however, that the cracks improved the gas flow into and out ofthe activated carbon matrix thereby improving the rates of refrigerantadsorption and desorption. Therefore the particular activated carbonmixture, the mixing, pressing and drying procedures prior to pyrolysis,and the temperature-time cycle of the pyrolysis, produced an improvedmatrix for gas diffusion without effecting integrality of theadsorbent-heat exchanger device.

The density of the activated carbon matrix was measured and determinedto be 0.36 g/cc. A density of at least about 0.3 g/cc is most useful inammonia-heat pump systems. The BET area of the activated carbon matrixwas about 2200 m² /g as estimated by a Thermal-Gravimetric-Analyzer testusing Refrigerant 22 ("R22") as the sotbate, see FIG. 2, and comparingthe adsorption with R22 onto Anderson AX-21 activated carbon without abinder, see FIG. 3. The known BET surface area of Anderson AX-21 isapproximately 3000 m² /g. Curves 22 and 32 represent temperature. Curves24 and 34 represent combined weight of adsorbent and refrigerant withthe change in weight representing sorption or desorption of refrigerant.

The dissolving agent can be isopropanol or other alcohols, or anysolvent for the binder employed. The pressing pressure for molding theactivated carbon mixture into the fin area of the unit can be increasedto increase the ultimate adsorbent density. The amount of resol bindercan be between 3% and 60% by weight of the dry activated carbon weight.The resol used for these tests was from a standard supply source ofA-stage phenol-formaldehyde resins. The resin is fusible, becoming aliquid on heating, and upon further heating is transformed into aninfusible, insoluble thermoset crosslinked polymer substance.

The heat transfer coefficient can be increased by placing an ullageelement 42, see FIG. 4, inside tube 44 to further constrict the heattransfer fluid to the inside diameter of the tube.

In mobile systems or other systems subject to vibration, added integritycan be achieved by painting a resol solution onto the outside surface ofthe activated carbon matrix and then re-pyrolyzing the unit. Acircumferential screen can also be added to the outside matrix surfacefor support. The mesh of the screen should be large enough to notinterfere with refrigerant adsorption and desorption rates to and fromthe adsorbent.

FIG. 5 represents a typical center section 50 of one embodiment of thisinvention having a stainless steel center tube 52 for strength and analuminum extrusion fin part 54 having annular member 56 and spiral woundfin 58. Spiral wound fin 58 is like the thread of a screw and is one finspirally disposed around tube 52. However, when viewed in cross section,spiral wound fin 58 forms a plurality of spaced apart fins, and istherefore usually referred to in the plural, i.e. as fins 58.

Fins 58 are extruded simultaneously with the annular member 58 anddirectly onto stainless steel center tube 52. Fins 58 extend outwardlyfrom, and are perpendicular to, axis 60 of stainless steel tube 52. Anactivated carbon matrix 62 is securely bound in spaces 84 between fins58 thereby forming an integral adsorbent-heat exchanger device.

The outside diameter of the fins and activated carbon matrix is betweenabout 1.5" and about 8", the fin thickness between about 0.005" andabout 0.05", and the wall thickness of annular member 56 between about0.01" and about 0.1". The distance between opposing fins is betweenabout 0.05" and about 0.5". The stainless steel inner tube 52 has anoutside diameter of between about 1" and about 7", and a wall thicknessof between about 0.02" and about 0.2". Metal parts 52 and 54 can be madeeasily and inexpensively.

FIG. 6 is a plot of actual test data of an adsorbent-heat exchangerdevice of this invention in which the activated carbon particles wereadjoined to each other and to the metal parts of the finned tube heatexchanger. The adsorbent-heat exchanger device of this invention wassimilar to that shown in FIG. 4 and had a length of 23". The heattransfer fluid was pressurized water at about 180° C. and operated at aflow rate of 0.1 gallons per minute. The sorbate was R134a which wasdesorbed at about 140 psia. The device achieved a nearly fully desorbedheated condition in only about 2 minutes.

This can be compared to the data presented in FIGS. 5 and 7 of U.S. Pat.No. 4,709,558 in which a finned tube heat exchanger containing anadsorbent, believed to be granular solid silica gel held in place bywipe nets 20 and 20' (see column 8, line 37) rather than adjoining ofthe granular adsorbent particles to each other and to the metal parts ofthe heat exchanger, appears to not even be close to steady state, i.e. anearly full heated condition, after 3.5 minutes. U.S. Pat. No. 4,709,558is hereby incorporated herein by reference.

FURTHER EXAMPLES

The following examples illustrate the successes and failures experiencedin tests which lead to the production of the improved adsorbent-heatexchanger device of this invention.

Example No. 1--Omission of Solvent

The binder was mixed directly with the activated carbon particles in anattempt to coat the particles with binder. In particular 2 g of resolwas mixed with 10 g of activated carbon particles. It was observed thatthe resol stuck together as a thick blob and could not be distributedthroughout the particles.

Example No. 2--Inadequate Distribution of Binder

A first mixture was prepared by mixing 6.3 g of isopropanol (hereinafterreferred to as "iso") as a solvent, with 300 g of resol as a binder,thereby forming a solvent-to-binder ratio of 0.021. A second mixture wasprepared by mixing 12 g of iso with 12 g of dry activated carbonparticles, thereby forming a solvent-to-carbon ratio of 1. The secondmixture was added to, and vigorously mixed with, the first mixture,thereby forming a solvent-to-carbon ratio of 1.53 and a binder-to-carbonratio of 25. Mixing was very difficult and even after 30 minutesvigorous mixing the resol was more concentrated in some places than inother places. It therefore was concluded that an adequately boundactivated carbon product would not be formed from this mixture uponpyrolysis.

Example No. 3--Pre-Saturation of Carbon with Solvent

A first mixture was prepared by mixing 40 g of iso, as a solvent, with16 g of resol as a binder thereby forming a solvent-to-binder ratio of2.5. A second mixture was prepared by mixing 200 g of iso with 150 g ofdry activated carbon particles, thereby forming a mixture having theconsistency of moist sand or nearly saturated carbon, with asolvent-to-carbon ratio of 1.33. The second mixture was added to, andvigorously mixed with, the first mixture, thereby forming a thirdmixture having a solvent-to-carbon ratio of 1.6 and a binder-to-carbonratio of 0.107. Thereafter 55 g of iso was added to, and vigorouslymixed with the third mixture thereby increasing the solvent-to-carbonratio to 1.97. About 20 g of iso was evaporated from the mixture to forma very thick tar thereby decreasing the solvent-to-carbon ratio to about1.83. This mixture was pressed under 1000 psi into the spaces betweenconsecutive spaced apart fins, then dried over night, and then pyrolyzedusing the following temperature-time heating sequence.

The finned tube heat exchanger member with the mixture filling thespaces between consecutive spaced apart fins was heated at a rate of100° C./hr to a temperature of 600° C. under a dry N₂ purge. It was thenmaintained at 600° C. for 18 hrs under the dry N₂ purge therebypyrolyzing the resol. The unit was then cool to room temperature.

Upon inspection of the unit the pyrolyzed product was found to be veryflaky and, therefore, was deemed to be unacceptable.

Example No. 4--Pro-Saturation of Carbon with Water

A first mixture was prepared by mixing 0.5 g of iso, as a solvent, with0.75 g of resol as a binder thereby forming a solvent-to-binder ratio of0.687. A second mixture was prepared by mixing 4.5 g of water with 3 gof dry activated carbon particles. The second mixture was added to, andvigorously mixed with,.the first mixture, thereby forming a thirdmixture having a solvent-to-carbon ratio of 0.167 and a binder-to-carbonratio of 0.25. Thereafter 6 g of iso was added to, and vigorously mixedwith, the third mixture thereby increasing the solvent-to-carbon ratioto 2.17. It was noticed that the binder did not adhere the activatedcarbon particles together. This mixture was pressed under 1000 psi, thendried over night, and then pyrolyzed using the temperature-time heatingsequence set forth in Example No. 3 above. The pyrolyzed product wasvery flaky and therefore was deemed to be unacceptable.

Example No. 5--Insufficient Binder

A first mixture was prepared by mixing 6 g of iso, as a solvent, with0.6 g of resol as a binder thereby forming a solvent-to-binder ratio of10. A second mixture was prepared by mixing 12 g of iso with 12 g of dryactivated carbon particles thereby forming a solvent-to-carbon ratioto 1. The second mixture was added to, and vigorously mixed with, thefirst mixture, thereby forming a third mixture having asolvent-to-carbon ratio of 1.5 and a binder-to-carbon ratio of 0.05.Thereafter 6 g of iso was added to, and vigorously mixed with, the thirdmixture thereby increasing the solvent-to-carbon ratio to 2 and forminga mixture having the consistency of loose tar. About 2 g of iso wasevaporated from the mixture thereby decreasing the solvent-to-carbonratio to about 1.8 and forming a mixture having the consistency of thicktar. This mixture was pressed under 1000 psi, then dried over night, andthen pyrolyzed using the temperature-time heating sequence set forth inExample No. 3 above. The pyrolyzed product was very flaky and thereforewas deemed to be unacceptable.

Example No. 6--Pressing as a Loose Tar

A first mixture was prepared by mixing 63 g of iso, as a solvent, with30 g of resol as a binder thereby forming a solvent-to-binder ratio of2.1. A second mixture was prepared by mixing 120 g of iso with 120 g ofdry activated carbon particles thereby forming a solvent-to-carbon ratioto 1. The second mixture was added to, and vigorously mixed with, thefirst mixture, thereby forming a third mixture having asolvent-to-carbon ratio of 1.53 and a binder-to-carbon ratio of 0.25.Thereafter 60 g of iso was added to, and vigorously mixed with, thethird mixture thereby increasing the solvent-to-carbon ratio to 2.03 andforming a mixture having the consistency of loose tar. Solvent was notevaporated from the mixture to form a thick tar. Rather the loose tarmixture was pressed under 1000 psi into the spaces between consecutivespaced apart fins. A large amount of solvent and binder was wrung out ofthe mixture during the pressing operation. The pressed mixture was thendried over night, and then pyrolyzed using the temperature-time heatingsequence set forth in Example No. 3 above. The pyrolyzed product wasmore flaky-than a corresponding sample (see Example No. 15 below) thatwas dried to a thick tar consistency prior to pressing and therefore wasdeemed to be less acceptable.

Example No. 7--Vibrating Mixture into Space between Fins

A first mixture was prepared by mixing 633 g of iso, as a solvent, with300 g of resol as a binder thereby forming a solvent-to-binder ratio of2.11. A second mixture was prepared by mixing 1200 g of iso with 1200 gof dry activated carbon particles thereby forming a solvent-to-carbonratio to 1. The second mixture was added to, and vigorously mixed with,the first mixture, thereby forming a third mixture having asolvent-to-carbon ratio of 1.53 and a binder-to-carbon ratio of 0.25.Thereafter 600 g of iso was added to, and vigorously mixed with, thethird mixture thereby increasing the solvent-to-carbon ratio to 2.02 andforming a mixture having the consistency of loose tar. About 150 g ofiso was evaporated from the mixture to form a mixture having theconsistency of thick tar. This mixture was placed on top of the finnedtube heat exchanger member and the heat exchanger member vibrated toflow the mixture into the spaces between fins. Plastic sheeting was usedto seal the bottom portion of the unit and retain the mixture betweenthe fins. The unit was then dried over night, and then pyrolyzed usingthe temperature-time heating sequence set forth in Example No. 3 above.The pyrolyzed product was flaky and therefore was deemed to beunacceptable.

Example No. 8--Pyrolysis at temperatures other than 600° C.

Pyrolysis at temperatures significantly higher than 600° C. will resultin weakening or melting of the aluminum fins and result in an unithaving a low heat transfer value and of no commercial value. Whilepyrolysis at temperatures significantly lower than 600° C. will resultin an incompletely pyrolyzed binder having a weakened structure, an unitin which ammonia refrigerant will react thereby contaminating therefrigerant, and hence result in an unit of no commercial value.

Example No. 9--Polyvinylidene Chloride as a Binder

Polyvinylidene chloride, available as a powdered solid, when used as abinder and mixed with activated carbon can not be sufficiently blendedwith the activated carbon so that when the mixture is pyrolyzed it willproduce a bonded adsorbent. Polyvinylidene chloride requires a monthlong pyrolysis thereby raising the cost of the unit to exorbitantlevels. Incompletely pyrolyzed polyvinylidene chloride generateshydrochloric acid vapors which corrode the unit and other parts of thesystem in which it is used.

Example No. 10--Carboxy Methylcellulose as a Binder

Carboxy methylcellulose or "Methocel" as a Binder will react withammonia unless pyrolyzed, and if pyrolyzed it does not have any bindingstrength. In either case, the unit will have no commercial value.

Example No. 11--Kaopolite Clay as a Binder

Kaopolite clay when used as a binder requires pyrolysis at a temperatureof about 1000° C. which exceeds the melting temperature of the aluminumfins of the unit and renders the unit no commercial value.

Example No. 12--Copper Fins

Copper fins will react with ammonia refrigerant and contaminate therefrigerant making the unit and system inoperable and of no commercialvalue.

Example No. 13--Stainless Steel Fins

Stainless steel fins have too low a thermal conductivity to conduct heatquickly and efficiently and therefore render the system in which theyare used of no commercial value.

Example No. 14--Zeolite, Silica or Alumina as Adsorbent

Use of zeolite, silica or alumina as the adsorbent lower the efficiencyof the unit and system because of their relatively low surface areacompared to activated carbon. These adsorbents are therefore notcommercially useful in heat pump system requiring high efficiency.

Example No. 15--Novel Process for Mixing and Pressing as a Thick Tar

After many attempts to produce a stable adsorbent from activated carbonparticles adjoined to each other and to the fins and outside diameter ofthe tube, some of which are described in Examples 1-14, we havediscovered and demonstrated a successful novel mixing process forforming a mixture of binder coated activated carbon particles having asolvent-to-activated carbon ratio of about 1.9 and a binder-to-activatedcarbon ratio of about 0.25 which has the consistency of a thick tar. Thethick tar was then pressed into the spaces between consecutive spacedapart fins of a finned tube heat exchanger member, dried further todecrease the solvent-to-carbon ratio to about 1.5 and then pyrolyzedusing the temperature-time heating sequence set forth in Example No. 3above to form a tightly bound activated carbon adsorbent adjoined to thealuminum fins of the finned tube heat exchanger member. Details of thisprocess for producing the integral adsorbent-finned tube heat exchangermember of this invention are set for in Table No. 1.

Analysis has demonstrated that the thusly produced integraladsorbent-heat exchanger units of this invention, when utilized in aheat pump system using ammonia as a refrigerant, enables a system highefficiency to be achieved. Analysis further demonstrates thatammonia-activated carbon heat pump systems using the finned tube heatexchanger member of this invention are very efficient and can competecommercially with standard freon based compressor systems.

FIGS. 7A and 7B are cross-sectional views which illustrate anotherembodiment of this invention, generally designated by numeral 70, inwhich the fin part, which comprises a plurality of fins 71, extends in adirection which is both perpendicular to, and longitudinal to, axis 72of the tube part 73. FIG. 7B is a view through line 7--7 of FIG. 7A. Inthis embodiment fins 71 extend outwardly from tube part 73. Fins 71 areseparate and distinct from each other. As in the embodiment in FIG. 4,an ullage element 42 fills a portion of the hollow central cavity 74.The spaces between fins 71 and outer surface 75 of the tube part arefilled with adsorbent 76, which is adjoined to the metal parts of theheat exchanger device thereby forming an integral adsorbent-heatexchanger device. When in use, refrigerant flows to and from theadsorbent through its outside surface 77 thereof, and heat transferfluid flow into and out of adsorbent-heat exchanger device through ports78 and 79.

FIGS. 8A and 8B are cross-sectional views which illustrate yet anotherembodiment of this invention, generally designated by numeral 80, inwhich the fin part, which comprises a plurality of fins 81 that alsoextend in a direction which is both perpendicular to, and longitudinalto, axis 82 of the tube part 83. FIG. 8B is a view through line 8--8 ofFIG. 8A. As in embodiment 70, fins 81 are separate and distinct fromeach other. However, in this embodiment the fins extend inwardly fromtube part 83. Spaces between fins 81 and the inner surface 85 of thetube part are filled with adsorbent 86 which is adjoined to the metalparts of the heat exchanger device thereby forming an integraladsorbent-heat exchanger device. When in use, refrigerant flow to andfrom inside cylindrical surface 84 of adsorbent 86 through ports 87 and88. Heat transfer fluid flow into and out of adsorbent-heat exchangerdevice 80 through ports 89 and 90 which are in the metal ends 92 of theshell part 94. Metal ends 92 are preferably welded to the shell part 94.Metal ends 96 are preferably welded to the annular part of tube part 83after placement of adsorbent 86 in the interior of the heat exchangerunit and adjoining or bonding of the adsorbent to the metal tube partsthereof.

While the preferred embodiments of the present invention have beendescribed, it should be understood that various changes, adaptations andmodifications may be made thereto without departing from the spirit ofthe invention and the scope of the appended claims. It should beunderstood, therefore, that the invention is not to be limited to minordetails of the illustrated invention shown in preferred embodiment andthe figures and that variations in such minor details will be apparentto one skilled in the art.

Therefore it is to be understood that the present disclosure andembodiments of this invention described herein are for purposes ofillustration and example and that modifications and improvements may bemade thereto without departing from the spirit of the invention or fromthe scope of the claims. The claims, therefore, are to be accorded arange of equivalents commensurate in scope with the advances made overthe art.

INDUSTRIAL APPLICABILITY

The adsorbent-heat exchanger devices of this invention are useful inheat pump systems used for air conditioning and heating rooms andbuildings in the summer and winter, respectively.

                                      TABLE NO. 1                                 __________________________________________________________________________                            Mixture:                                                                      First                                                                              Sec'd                                                                              Third                                                               Ratio:                                                 PROCEDURE                                                                                             ##STR1##                                                                           ##STR2##                                                                           ##STR3##                                                                           ##STR4##                              __________________________________________________________________________    A.                                                                              First Mixture: Add 633 g isopropanol                                                                2.11                                                    ("iso") to 300 g pure resol and mix.                                        B.                                                                              Second Mixture: Add 1200 g iso to 1200 g dry                                                             1.00                                               activated carbon particles ("ACP").                                         C.                                                                              Add second mixture (B) to first mixture (A)                                                                   1.53 0.25                                     and mix thereby forming third mixture.                                      D.                                                                              Add 600 g iso to third mixture (C) to give                                                                    2.02 0.25                                     the consistency of loose tar.                                               E.                                                                              Dry mixture from (D) with a hot air gun to                                                                    1.90 0.25                                     evaporate 150 g of iso from mixture to give                                   the consistency of thick tar.                                               F.                                                                              Press mixture from (E) in between fins of                                                                     1.90 0.25                                     finned tube heat exchanger member by                                          inserting in a mold pressurizing at a                                         pressure of at least 500 psi pressure.                                      G.                                                                              Drying the finned tube heat exchanger member                                                                  1.49 0.25                                     from (F) at room temperature for 6 days to                                    evaporate 500 g of iso.                                                     H.                                                                              Heating the finned tube heat exchanger                                                                        0    0                                        member from (G) at a rate of 100° C./hr to                             600° C. under a dry N.sub.2 purge, maintain at                         600° C. for 18 hrs. under dry N.sub.2 purge thereby                    pyrolyzing the resol, and then cool to room                                   temperature.                                                                I.                                                                              Paint a 50/50 iso/resol solution onto outs-                                   ide surface of activated carbon.                                            J.                                                                              Re-pyrolyze as in (H).                                                      K.                                                                              Scrape off any residual paralyzed resol                                       coating on outside surface that has flaked                                    or is loose thereby improving the adsorption                                  characteristic of the activated carbon                                        adjoined to the finned tube heat exchanger                                    member.                                                                     __________________________________________________________________________

What is claimed is:
 1. An integral apparatus for the transfer of heatcomprising:a finned tube heat exchanger member having a tube part and afin part, the fin part being in direct contact with the tube part andoutwardly thereof, the fin part forming a plurality of spaced apart finsand spaces along the tube part between the fins; and a bonded, pyrolyzedactivated carbon adsorbent matrix formed from a mixture comprisingactivated carbon particles and resol binder, the matrix being in thespaces, adjoined to the fins and the tube part to form an integralapparatus capable of withstanding repetitive adsorption and desorptioncycles without the matrix becoming unbonded and without the matrixbecoming unadjoined from the fins and the tube part.
 2. The integralapparatus of claim 1, wherein the fin part is aluminum.
 3. The integralapparatus of claim 1, wherein the tube part is aluminum.
 4. The integralapparatus of claim 1, wherein the activated carbon selected from thegroup consisting of activated carbon particles, activated carbongranules, pre-shaped activated carbon forms, and mixtures thereof. 5.The integral apparatus of claim 1, wherein the tube part is stainlesssteel.
 6. The integral apparatus of claim 4, wherein the fin part of thefinned tube heat exchanger member is aluminum and comprises an annularmember, which surrounds the tube part, and to which the plurality ofspaced apart fins are attached, and wherein the fins extend from theannular member in a direction perpendicular to the axis of the tubepart.
 7. The integral apparatus of claim 1, wherein the fins extend in adirection perpendicular to the axis of the tube part.
 8. The integralapparatus of claim 1, wherein the activated carbon adsorbent comprisespre-shaped activated carbon forms made from activated carbon particles.9. The integral apparatus of claim 1, wherein the fins extend in adirection perpendicular to, and longitudinal to, the axis of the tubepart.
 10. An integral apparatus for the transfer of heat comprising:afinned tube heat exchanger member having a tube part and a fin part, thefin part being in direct contact with the tube part and outwardlythereof, the fin part forming a plurality of spaced apart fins andspaces along the tube part between the fins; and a bonded, pyrolyzedactivated carbon adsorbent matrix in the spaces, the adsorbent matrixadjoined to the fins and the tube part by a process which comprisesplacing a mixture comprising activated carbon particles and resol binderinto the spaces, and thereafter, subjecting the apparatus with themixture in the spaces to an elevated temperature operable for causingthe resol binder to bond the activated carbon particles together to formthe adsorbent matrix and to adjoin the activated carbon adsorbent matrixto the fins and to the tube part thereby producing an integral apparatusfor the transfer of heat, the integral apparatus being capable ofwithstanding repetitive adsorption and desorption cycles without theactivated carbon particles becoming unbonded and without the matrixbecoming unadjoined from the fins and the tube part.
 11. The integralapparatus of claim 10, wherein the elevated temperature is between about400° C. and about 600° C.
 12. The integral apparatus of claim 10,wherein the elevated temperature is effected by heating the apparatus ata rate of about 100° C./hr under a non-deleterious atmosphere until apeak temperature of about 600° C. is reached, and thereafter,maintaining the apparatus at the peak temperature for about 10 to about20 hrs.
 13. An integral apparatus for the transfer of heat comprising:afinned tube heat exchanger member having a tube part and a fin part, thefin part being in direct contact with the tube part and outwardlythereof, the fin part forming a plurality of spaced apart fins andspaces along the tube part between the fins; and a bonded, pyrolyzedactivated carbon adsorbent matrix in the spaces, the adsorbent matrixadjoined to the fins and the tube part by a process which comprisesplacing a mixture which comprises a resol binder having a carbon basedmolecular structure, and particles of activated carbon, into the spaces,and thereafter, subjecting the apparatus with the mixture in the spacesto an elevated temperature operable for pyrolyzing the binder, and forbonding the activated carbon particles to each other to form theadsorbent matrix and to adjoin the adsorbent matrix to the fins, and tothe tube part thereby producing an integral apparatus for the transferof heat, the integral apparatus being capable of withstanding repetitiveadsorption and desorption cycles without the activated carbon particlesbecoming unbonded and without the matrix becoming unadjoined from thefins and the tube part.
 14. The integral apparatus of claim 13, whereinthe placing of the mixture into the spaces comprises pressing themixture under an elevated pressure of at least about 690 kPa (100 psi).15. An integral apparatus for the transfer of heat comprising:a finnedtube heat exchanger member having a tube part and a fin part, the finpart being in direct contact with the tube part and outwardly thereof,the fin part forming a plurality of spaced apart fins and spaces alongthe tube part between the fins; and a bonded, pyrolyzed activated carbonadsorbent matrix in the spaces, the adsorbent matrix adjoined to thefins and the tube part by a process which comprisespressing a mixturewhich comprises a resol binder having a carbon based molecularstructure, a solvent for the binder, and particles of activated carbon,into the spaces, thereafter, removing an effective amount of the solventfrom the mixture operable for allowing the mixture to be pyrolyzed to adensity of at least about 0.3 g/cc, and thereafter, subjecting theapparatus with the mixture in the spaces to an elevated temperatureoperable for pyrolyzing the binder, and for bonding the activated carbonparticles to each other to form the adsorbent matrix and to adjoin theadsorbent matrix to the fins, and to the tube part thereby producing anintegral apparatus for the transfer of heat, the integral apparatusbeing capable of withstanding repetitive adsorption and desorptioncycles without the activated carbon particles becoming unbonded andwithout the matrix becoming unadjoined from the fins and the tube part.16. The integral apparatus of claim 15, wherein the solvent is selectedfrom the group consisting of alcohols, ketones and mixtures thereof. 17.The integral apparatus of claim 15, wherein the solvent is isopropanol.18. An integral apparatus for the transfer of heat comprising:a finnedtube heat exchanger member having a tube part and a fin part, the finpart being in direct contact with the tube part and outwardly thereof,the fin part forming a plurality of spaced apart fins and spaces alongthe tube part between the fins; anda bonded, pyrolyzed activated carbonadsorbent matrix in the spaces, the adsorbent matrix adjoined to thefins and the tube part by a process which comprisesa. forming a firstmixture which comprises a resol binder having a carbon based molecularstructure and a solvent for the finder, b. forming a second mixturewhich comprises a solvent and particles of activated carbon, c. addingan effective amount of the first mixture to the second mixture operablefor causing the first mixture to wet the activated carbon particles ofthe second mixture thereby forming a third mixture, d. removing aneffective amount of solvent from the third mixture operable forproducing a mixture of lower solvent content which can be pressed intothe spaces without exuding a large amount of solvent, e. pressing themixture of lower solvent content into the spaces, thereafter and withthe mixture pressed into the spaces, f. removing an effective amount ofsolvent from the mixture operable for allowing the mixture to bepyrolyzed to a density of at least about 0.3 g/cc while remaining in thespaces, and thereafter, g. subjecting the apparatus with the mixture inthe spaces to an elevated temperature operable for pyrolyzing thebinder, and for bonding the activated carbon particles to each other toform the adsorbent matrix and to adjoin the adsorbent matrix to thefins, and to the tube part thereby producing an apparatus for thetransfer of heat, the integral apparatus being capable of withstrandingrepetitive adsorption and desorption cycles without the activated carbonparticles becoming unbonded and without the matrix becoming unadjoinedfrom the fins and the tube part.
 19. The integral apparatus of claim 18,wherein the process for adjoining the adsorbent to the fins and the tubepart further comprises, after step (c) and before step (d),adding aneffective amount of a solvent to the third mixture formed in step (c) toadjust the viscosity of the mixture to between about 10,000 and about500,000 poise.
 20. The integral apparatus of claim 19, wherein theprocess for adjoining the adsorbent to the fins and the tube partfurther comprises:adjusting the weight ratio of binder-to-activatedcarbon in step (c) to a value between about 0.05 and about 0.5,adjusting the weight ratio of solvent-to-activated carbon in step (c) toa value between about 0.5 and about 6, and adjusting the weight ratio ofsolvent-to-binder in step (c) to a value between about 6 and about 10.21. The integral apparatus of claim 18, wherein the process foradjoining the adsorbent to the fins and the tube part further comprisesafter step (g),painting a solvent containing dissolved resol on theoutside surface of the adsorbent, and thereafter, subjecting theapparatus to an elevated temperature operable for pyrolyzing the resolon the outside surface.
 22. The integral apparatus of claim 18, whereinthe process for adjoining the adsorbent to the fins and the tube partfurther comprises, after step (c) and before step (d),adding aneffective amount of a solvent to the third mixture formed in step (c) toadjust the viscosity of the mixture to between about 10,000 and about500,000 poise, after step (g), painting a solvent containing dissolvedresol in a solvent on the outside surface of the adsorbent, andthereafter, subjecting the apparatus to an elevated temperature operablefor pyrolyzing the resol on the outside surface.
 23. The integralapparatus of claim 18, wherein the process for adjoining the adsorbentto the fins and the tube part further comprises adjusting the weightratio of solvent-to-binder in step (a) to a value between about 0.5 andabout
 10. 24. The integral apparatus of claim 18, wherein the processfor adjoining the adsorbent to the fins and the tube part furthercomprises adjusting the weight ratio of solvent-to-activated carbon instep (b) to a value between about 0.1 and about
 5. 25. The integralapparatus of claim 18, wherein the process for adjoining the adsorbentto the fins and the tube part further comprises adjusting the weightratio of binder-to-activated carbon in step (c) to a value between about0.05 and about 0.5.
 26. The integral apparatus of claim 18, wherein theprocess for adjoining the adsorbent to the fins and the tube partfurther comprises:adjusting the solvent-to-binder weight ratio in step(a) to a value between about 1.8 and about 2.4, adjusting thesolvent-to-carbon weight ratio in step (b) to a value between about 0.7and about 1.3, adjusting the binder-to-carbon weight ratio in step (c)to a value between about 0.2 and about 0.3, adding, after step (c) andbefore step (d), an effective amount of a solvent to the third mixtureformed in step (c) to adjust the solvent-to-carbon weight ratio to avalue greater than about 1.9 but less than about 2.3, and adjusting thesolvent-to-carbon weight ratio in step (d) to a value at least about 1.7but less than about
 2. 27. The integral apparatus of claim 18, whereinthe process for adjoining the adsorbent to the fins and the tube partfurther comprises:adjusting the solvent-to-binder weight ratio in step(a) to a value between about 2 and about 2.2, adjusting thesolvent-to-carbon weight ratio in step (b) to a value between about 0.9and about 1.1, adjusting the binder-to-carbon weight ratio in step (c)to a value between about 0.22 and about 0.28, adding, after step (c) andbefore step (d), an effective amount of a solvent to the third mixtureformed in step (c) to adjust the solvent-to-carbon weight ratio to avalue greater than about 2 but no greater than about 2.2, and adjustingthe solvent-to-carbon weight ratio in step (d) to a value less thanabout 1.95.
 28. An integral apparatus for the transfer of heatcomprising:a finned tube heat exchanger member having a tube part and afin part, the fin part being in direct contact with the tube part andinwardly thereof, the fin part forming a plurality of spaced apart finsand spaces along the tube part between the fins; and a bonded, pyrolyzedactivated carbon adsorbent matrix formed from a mixture comprisingactivated carbon particles and resol binder, the matrix being in thespaces, adjoined to the fins and the tube part to form an integralapparatus capable of withstanding repetitive adsorption and desorptioncycles without the matrix becoming unbonded and without the matrixbecoming unadjoined from the fins and the tube part.
 29. The integralapparatus of claim 28, wherein the fins extend in a directionperpendicular to, and longitudinal to, the axis of the tube part.